U.S. Pat. Nos. 3,391,363, 3,548,354, and 4,028,653 all disclose transformers having radial cooling channels with means for guiding cooling fluid through the channels.
Like the cooling duct arrangement described in the aforementioned patents, most cooling ducts consist of spaces arranged between the winding sections in a transformer that allow for the continuous flow of cooling oil through the individual windings section for cooling and insulating purposes. The inner insulating oil barrier generally comprises the wall of the winding cylinder and the outer oil insulating barrier consists of a cylinder that encompasses the winding. In order to cause the oil to flow in a labyrinth pattern between the individual windings sections, the outer oil block is positioned against the outer barrier on one side and a passageway is provided between the opposite end of the outer oil block and the inner insulating barrier. The inner oil block is positioned against the inner insulating barrier such that a passageway is provided between the other end of the inner oil block and the outer barrier to allow for the passage of oil. During the transformer drying process, there is a tendency for the inner insulating barrier which is usually the winding cylinder, to shrink away from the winding and leave a space between the inner oil block and the inner insulating barrier. This space allows some of the oil to transfer directly up along the inner insulating barrier rather than flow in a labyrinth path between the windings causing a nonuniform distribution of cooling oil.
The purpose of this invention is to provide an inner oil block arrangement wherein the inner oil block does not move away from the inner insulating barrier during the transformer drying process.